Patent GB-829023-A (GB)
Title: Method of coating a surface with poly-per-halocarbon resin and article formed thereby
IPC: C09D127/12
Filed: 1956-11-20
Abstract: A surface is coated by applying thereto at least one coat of a composition comprising a uniform aqueous or non-aqueous dispersion of a normally solid poly-per-halocarbon resin having a particle size in the range of 0.1 to 3 microns, and a non-poly-per-halocarbon extender resin compatible therewith and suspended or dissolved in an organic solvent, the poly-per-halo-carbon resin comprising 5 to 70% and the extender resin 95 to 30% by weight of the total resin content, pre-baking the coat at substantially below the fusion temperature of the poly-per-halocarbon resin, applying at least one further coating of similar composition but with a greater proportion of poly-per-halocarbon resin, and heating sufficiently to fuse the last-mentioned resin and form a film strongly adhering to the underlying film.  An initial coat, the resin content of which is substantially pure extender resin, and a final coat, of which it is substantially pure poly-per-halocarbon resin, may be applied; or coats containing both types of resin may be alternated with coats containing only poly-per-halocarbon resin. Poly-per-halocarbon resins mentioned include polytetrafluoroethylene, polytrifluorochloroethylene, polydifluorodichloroethylene, and similar resins wherein chlorine is replaced by bromine or iodine; polypolyhalocyclobutenes such as polypentafluorochlorocyclobutene and polytetrafluorodichlorocyclobutene; and the pyrolysis products of unsaturated polyfluoro- or polyfluorochloro-ethylenes.  The extender resins may be (a) condensation polymers of epichlorhydrin and bisphenol, which may be modified with high molecular weight fatty acids, resin acids or polybasic acids; (b) phenol aldehyde resins, which may be modified with, e.g. rosin, rosin esters, or polybasic acid esters; (c) silicones and modified silicones, e.g. silicone alkyd resins; (d) furane resins; (e) polyvinyl compounds such as polymers and copolymers of vinyl acetate and vinyl chloride, or of polyvinyl alcohol and polyvinyl chloride with modifying agents such as polybasic acids or anhydrides; (f) urea-formaldehyde and alcohol-modified urea-formaldehyde resins; (g) condensation products of a polybasic acid or anhydride and a polyhydroxy-alcohol such as glycerol, which may be modified by rosin esters or fatty acids; (h) resins formed by condensing melamine and urea, melamine and formaldehyde, or melamine, formaldehyde and urea, which may be modified by esterifying compounds such as higher alcohols.  The mixtures of poly-per-halocarbon resins and extender resins may be produced by (a) milling a mixture of the solid resins with a suspending agent or (b) preparing separately suspensions of poly-per-halocarbon resins and either suspensions or solutions of the extender resin, and mixing them.  Plasticizers such as poly-per-halocarbon oils or waxes and pigments and fillers, may be included.  The compositions may be applied by spraying or brushing to the interior of pipes, reaction vessels, fume ducts, storage tanks, vats and the like, or to smaller articles by dipping. Valves wire, panels, antifriction bearings and baking tins may also be coated. The surface to be coated, which may be iron, steel, ferrous alloy, aluminium, copper, stone, ceramic or plastic (if sufficiently heat-resistant), may be pre-treated by sand-blasting or acid etching, and may be primed with a primer suitable for use with the extender resin.  One or more coatings of a baking resin, which is preferably the same as the extender resin, may be applied and pre-baked, preferably below its curing temperature; coats of compositions comprising increasing proportions of polyhalocarbon resin are then applied, with drying, and pre-baking, to a temperature above the fusion point of the poly-per-halocarbon resin, where this amounts to more than 25% of the resin content, are then applied.  Finally, coatings containing 100% of poly-per-halocarbon resin are applied, and the article is given a final bake.  In a modification, a sand-blasted steel panel is given twelve alternate coatings of a composition having a ratio of poly-per-halocarbon to extender resin of 60 : 40 and of 100% poly-per-halocarbon resin, with three final coats of the latter, with intermediate pre-bakings and a final bake. Heat-resistant fabrics of, e.g., glass, asbestos, synthetic resin or metal may be coated, e.g. polytetrafluoroethylene, an initial coating of an extender resin or a mixture thereof with a poly-per-halocarbon resin being first applied.  For example, a mixture containing polytrifluorochloroethylene and an extender resin may first be applied by dipping, spraying or roller-coating, followed by coatings containing polytetrafluoroethylene and an extender resin and polytetrafluoroethylene alone, with intermediate bakings; the surface is then subjected to flaming. An adhesive, e.g. a phenolic, epoxy or "Hycar" (Registered Trade Mark) resin may be applied to the uncoated side.  The resulting fabric may be applied to surfaces such as the interior of tanks, to protect them from corrosion.ALSO:A coating composition comprises a uniform aqueous or non-aqueous dispersion of a normally solid poly-per-halocarbon resin having a particle size in the range of 0.1 to 3 microns, and a non-poly-perhalocarbon extender resin compatible therewith and suspended or dissolved in an organic solvent, the poly-per-halocarbon resin comprising 5 to 70% and the extender resin 95 to 30% by weight of the total resin content. Poly-per-halocarbon resins mentioned include polytetrafluoroethylene, polytrifluorochloroethylene, polydifluorodichloroethylene and similar resins wherein chlorine is replaced by bromine or iodine; poly-polyhalocyclobutenes such as polypentafluorochlorocyclobutene and polytetrafluorodichlorocyclobutene; and the pyrolysis products of unsaturated polyfluoro- or polyfluorochloroethylenes.  The extender resins may be (a) condensation polymers of epichlorhydrin and bisphenol, which may be modified with high molecular weight fatty acids, resin acids or polybasic acids; (b) phenol aldehyde resins, which may be modified with, e.g., rosin, rosin esters, or polybasic acid esters; (c) silicones and modified silicones, e.g. silicone alkyd resins; (d) furane resins; (e) polyvinyl compounds such as polymers and copolymers of vinyl acetate and vinyl chloride, or of polyvinyl alcohol and polyvinyl chloride with modifying agents such as polybasic acids or anhydrides; (f) urea-formaldehyde and alcohol-modified urea-formaldehyde resins; (g) condensation products of a polybasic acid or anhydride and a polyhydric alcohol such as glycerol, which may be modified by rosin esters or fatty acids; (b) resins formed by condensing melamine and urea, melamine and formaldehyde, or melamine, formaldehyde and urea, which may be modified by esterifying compounds such as higher alcohols.  The mixtures of poly-per-halocarbon resins and extender resins may be produced by (a) milling a mixture of the solid resins with a suspending agent or (b) preparing separately suspensions of the poly-per-halocarbon resins and either suspensions or solutions of the extender resins, and mixing them.  Specified solvents are toluene, xylene, acetone, diisobutyl ketone and butyl "Cellosolve" (Registered Trade Mark).  Sulphuric and phosphoric acids are also included in some examples.  Plasticizers such as poly-per-halocarbon oils or waxes, and pigments and fillers, e.g. chrome oxide, may be included.